Re: The Langevin's traveler

Le 02/08/2024 à 16:09, hitlong@yahoo.com (gharnagel) a écrit :

On Thu, 1 Aug 2024 21:14:29 +0000, Richard Hachel wrote:

Very pretty pictures but sorry, old friend, they are incorrect.

 C'est parfaitement correct. 

First of all, the time between Earth and Tau Ceti need not be 12 years. Just
how would an expedition to TC measure time?  Since a time at TC is
specified,
we must assume an earlier expedition arrived there.  One way to set the
time
there would be to carry their chronometer with them, which began the
journey
synchronized with Earth time.  Let's say they left Earth in 1960.  At
0.8c,
their time of arrival would be 1969 (ignoring acceleration and
deceleration).

 Absolutely.
I beg you to breathe and blow.
When dealing with Dr. Hachel, you must first listen to him and then respond with control.
It is true that in your example (departure 1960, speed Vo=0.8c) the rocket will arrive with a watch that will mark 1969.
Everyone says the same thing, and so do I.
I say that FOR the rocket, the rocket's watch marks 1969.
I say that FOR the earth, the rocket's watch marks 1969.
That is LOGICAL.
BUT two other questions will arise:
1. What time is it on earth FOR the rocket when the fact happens?
2. What time is it on earth FOR the earth when the fact happens?
These two questions are very different, and already require much more attention than the first two, because the answers given are most often wrong (since the bigwigs of physics do not understand THEIR theory correctly).

Earth time would be 1975.  So TC time would be behind Earth time by 6
years,
not 12 years.

 No.
 You do not understand your own example.
In your example, when the rocket reaches its goal,
we neglect the short-term accelerations, Stella's watch marks 1969. It crossed the 12 ly in 9 years of proper time.
But the terrestrial watch FOR the earth marks 1987!!!
The fact takes place in 1987 (and not in 1975) as one stupidly thinks when one understands nothing, but nothing at all of Hachel's work for 40 years on the simple and coherent geometry of the RR.
 R.H.